This invention relates to a novel process for removing halogenated hydrocarbons from dilute, halogenated hydrocarbon-containing aqueous fluids. More particularly, this invention relates to a novel process for removing trace amounts of halogenated hydrocarbons, such as 1,2-dichloroethane, 1,1-dichloroethane, 1,1,2,2-perchloroethylene, 1,1,2-trichloroethane, ethylene dibromide, methylene bromide and the like from contaminated ground water.
Methods for the removal of trace hydrocarbons from aqueous and vapor streams are extensive and vary widely. For example, U.S. Pat. No. 4,495,056 teaches steam stripping, carbon adsorption, biological treatment, and activated sludge treatment to purify water. Beall, U.S. Pat. No. 4,517,094, teaches adsorption of organic contaminants on two media: (1) organoclay and (2) granulated carbon. Von Klock et al., U.S. Pat. No. 5,106,507, utilize a stripping gas and a bed of activated carbon to remove hydrocarbon contaminants. Miller, U.S. Pat. No. 4,892,664, provides a method for decontaminating water which is contaminated by small concentrations of dissolved volatile organic compounds, the method comprising introducing the contaminated water into an air stripping column wherein the contaminants are stripped with air, pretreating the organic compounds-carrying air in a preheater, and passing the heated air through a catalytic stage that oxidized the organic compounds. U.S. Pat. No. 4,544,488 discloses the use of an induced draft air stripper and carbon adsorption bed to remove volatile organic chemical from water.
Carberry, U.S. Pat. No. 4,846,934 and U.S. Pat. No. 4,966,654 discloses a system for removing hydrocarbon contaminants from groundwater and moisture-laden soil. The system of Carberry comprises a steam stripping tower which is operated at subatmospheric pressure, a series of condensers and separators, and finally a carbon adsorber to remove any remaining uncondensed hydrocarbon contaminants.
Robbins, U.S. Pat. No. 4,236,973, utilizes a vapor such as air or steam to strip organic contaminants having a boiling point in excess of 200.degree. C. from pH adjusted water. Once stripped, the stripping vapor and organic contaminants can be passed into a scrubber wherein the vapor and contaminants are contacted with a stream of caustic or other material which preferentially absorbs the contaminants from the vapor.
Robbins, U.S. Pat. No. 4,783,242, describes a distillation system for removing vaporizable components from an aqueous medium comprising: a distillation column using steam to vaporize the vaporizable components, a condenser means to condense at least a portion of the vapor from the distillation column, a separator means to separate vapor from a recirculated fluid in the separator means, and a thermal compressor means to remove vapors from the separator means and inject motive steam into the column. According to Robbins, the vaporizable components include trichloroethane, propylene chlorohydrin, bromine, methylene chloride, benzene, toluene, and mixtures thereof.
McGill, U.S. Pat. No. 3,898,058, provides a process for removal of hydrocarbons by the application of a vacuum to a contacting vessel in which a contaminated water stream is caused to flow across packing material or trays for efficient gas removal. The removed hydrocarbon materials are then compressed, condensed and further separated to remove gaseous and/or liquid hydrocarbons from the system.
While the foregoing provide a multitude of methods for removal of contaminants from groundwater, there continues to be a need for efficient, yet cost effective means for reducing groundwater contaminants while at the same time reducing the amount of contaminants discharged to the atmosphere.